1. Field of the Invention
The present invention relates to an optical image stabilizer for a camera module assembly, in which one or more guide portions for guiding linear movement while preventing friction are provided in first and second drive portions.
2. Description of the Related Art
With the recent proliferation of digital still and video cameras, there is an increasing demand for photographing high-quality still and moving pictures. In particular, a Complementary Metal Oxide Semiconductor (CMOS) sensor has replaced a Charge Coupled Device (CCD) sensor as a photographing device for a digital camera, because although the CCD sensor is superior to the CMOS sensor in terms of image quality, the CMOS sensor consumes less power and has a simpler structure. Accordingly, the market share of the CMOS sensor is increasing and recently, the image quality of the CMOS sensor has also improved. Along with the development of image sensors such as the CCD and CMOS sensors, the use of digital cameras has become common and a camera module is now installed in a portable terminal such as a cellular phone.
When the CMOS sensor is used, the resolution of a picture significantly degrades due to a hand-shake of the picture taker (user). Therefore, the use of an optical image stabilizer is increasing to prevent the resolution of a picture from degrading due to external vibrations or a hand-shake of a user.
A conventional optical image stabilizer for a camera module assembly may be one that drives an image sensor or performs stabilization by driving a lens. The optical image stabilizer may be controlled by a stepping motor drive system or a Voice Coil Motor (VCM) actuator system.
The VCM actuator system can be found in Korean Patent Publication No. 2006-122237 which discloses an optical image stabilizer.
The disclosed optical image stabilizer is structured such that an X-axis drive permanent magnet and coil and a Y-axis drive permanent magnet and coil are disposed at the edge of an optical lens, a drive frame and a ball bearing for supporting driving of the permanent magnets and coils are provided, and a current is applied to the X-axis drive permanent magnet and coil and the Y-axis drive permanent magnet and coil based on the amount of blurring of an object to drive the optical lens by a hand-shake displacement amount with an electromagnetic force.
Although the conventional optical image stabilizer for the camera module assembly includes a ball bearing for supporting linear movement, it is limited in regards to precisely controlling linear movement along an X-axis and a Y axis only with the ball bearing. To solve the problem, if a plurality of ball bearings are provided in the optical image stabilizer, the structure (thickness) of the drive portion becomes large and complicated, making it difficult to implement a camera module assembly for a subminiature digital camera and a portable terminal.
Accordingly, there is a need for an additional guiding device for supporting a drive function of an existing ball bearing.